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isValidHttpDate

Signature

Section titled “Signature”
isValidHttpDate(value: string): boolean

Return true when value is a real HTTP header date: the RFC 9110 §5.6.7 HTTP-date that headers like Last-Modified, Date and Expires carry, such as Fri, 15 Mar 2024 14:30:00 GMT.

  • True exactly when parseHttpDate returns a UTC string for the same value: the validator calls the parser, so the two cannot disagree.
  • All three HTTP-date formats, which RFC 9110 §5.6.7 says a recipient “MUST accept”: IMF-fixdate, and the obsolete rfc850-date (Sunday, 06-Nov-94 08:49:37 GMT) and asctime-date (Sun Nov 6 08:49:37 1994). The httpDate pattern matches IMF-fixdate alone.
  • Checks the calendar as well as the shape. The pattern matches a day that does not exist: 31 Feb, 29 Feb 2023 and 31 Jun are false here.
  • The day name must match the date, in all three formats. The pattern does not check it.
  • False for an hour above 23 and a minute above 59, which the pattern matches. False for a second of 60: GMT rejects leap seconds.
  • HTTP-date is case-sensitive and fixed-width, and its zone is the literal GMT: a numeric offset is false.
  • An rfc850-date reads the clock. Its two-digit year is read against the current instant (Temporal.Now.instant()), as parseHttpDate describes, so the same string can change its answer decades apart; if the clock cannot be read the answer is false. The other two formats never read the clock.
  • False for a non-string. Read the value with parseHttpDate; write one with formatHttpDate.

Parameters

Section titled “Parameters”
ParameterTypeDescription
valuestringcandidate RFC 9110 HTTP-date string

Returns

Section titled “Returns”

boolean indicating validity

Examples

Section titled “Examples”
import { isValidHttpDate } from "@northguild/gmt/utc/validate";


isValidHttpDate("Fri, 15 Mar 2024 14:30:00 GMT") // true
output 

Source

Section titled “Source”

utc/validate/isValidHttpDate.ts